RSR 13 is a synthetic allosteric modifer of hemoglobin. It decreases the oxygen affinity of hemoglobin and augments oxygen unloading in the microvasculature which increases the oxygen diffusion gradient to the tissues. By increasing tissue oxygenation, RSR 13 may reduce tumor hypoxia and enhance the cytotoxic effects of radiation therapy used to treat cancer patients with solid tumors. This study will therefore evaluate the safety and toxicity of this new agent and its efficacy.